Basic CS-Networks [Redpine Infotech Placement]: Sample Questions 1 - 2 of 3

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Question 1

Networks
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Describe in Detail

Essay▾

What is the use of ARP in TCP/IP stack?

Explanation

  • TCP/IP network has two addresses, one is physical and other is logical.
  • TCP/IP network has two addresses, one is physical and other is logical.
  • ARP provides bridge between these two addresses.
  • Address resolution protocol (ARP) maps an internet protocol address (IP address) to a physical machine address.
  • The ARP helps the IP directing datagrams to the exact receiving host by mapping the Ethernet addresses to known IP addresses.
  • ARP is a dynamic resolution protocol used to match IP addresses to data link layer addresses.
  • Lies in between data link layer and internet layer.
  • Physical machine address is recognized in the local network.
  • ARP is used as network layer protocol in the TCP/IP internet protocol.
  • It is an important address resolution protocol.
  • TCP protocol support is not always required in embedded uses of Internet technologies.
  • The ARP protocol is just one component of a TCP/IP.

Question 2

Networks
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Describe in Detail

Essay▾

What is the mechanism used for error detection in Data Link Layer?

Explanation

Define Error Detection and Its Method
  • Error in the received frames is detected by Parity check and CRC (cyclic redundancy) .

Parity Check

  • One extra bit is sent with the original bits to make number of 1s either even, in case of even parity or odd, in case of odd parity.
  • The sender while creating a frame counts the number of 1s in it.
  • For example, if even parity is used and number of 1s is even then one bit with value 0 is added.
  • This way numbers of 1s remain even.
  • The number of 1s is odd; to make it even a bit with value 1 is added.
The Number of 1s is Odd
  • The receiver simply counts the number of 1s in a frame.
  • If the count of 1s is even and even parity is used the frame is considered to be not-corrupted and is accepted.
  • If the count of 1s is odd and odd parity is used, the frame is still not corrupted.

CRC

  • CRC is based on binary division.
  • A sequence of redundant bits called cyclic redundancy check bits are the end of data unit so the resulting data unit becomes exactly divisible by a second binary number.
  • The destination, the incoming data unit is divided by the same number.
  • If at this step there is no remainder, the data unit is assumed to be correct and is therefore accepted.
  • A remainder indicates that the data unit has been damaged in transit and therefore must be rejected.

    For example,

The CRC Divisor
  • The receiver performs division operation on code words using the same CRC divisor.
  • Only if remainder contains all zeros the data bits are accepted.

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